A Multi-hop Mobile Networking Test-bed for Telematics Carnegie Mellon University: Rahul Mangharam (Speaker) Jake Meyers, Raj Rajkumar, Dan Stancil {rahulm, jjmeyers, raj, General Motors: Jay Parikh, Hariharan Krishnan, Chris Kellum {jayendra.s.parikh, hariharan.krishnan, April 2005

Network Protocol Design Multi-hop Wireless Test-bed Vehicular Networking Applications What this talk is about Wireless Channel & Protocol Performance Bottom-Up Approach Top-Down Approach

O u t l i n e 1.The Need for Wireless Vehicular Networking 2.Unique Multi-hop Protocol Design Challenges 3.GrooveNet - Geographic Routing 4.Vehicular Networking Test-bed 5.On-road Communication Performance Analysis 6.Multi-hop Wireless Vehicular Applications

Experimental Ad Hoc Test-bed Mobile Node Internet V Remote Monitoring of Experiment 1XRTT Cellular Data Network GPS Differential GPS reference station beacons 1.Vehicle-to-Vehicle Multi-hop 2.Vehicle-to-Mobile Gateway 3.Vehicle-to-Infrastructure 5.9 GHz DSRC Dedicated Short Range Communications Between vehicles

Vehicular Networking Application Categories 1.Safety Alerts –Sudden Breaking –Airbag deployment –Skidding 2.Traffic Congestion Probing –Travel Time –Dynamic Route Planning –Road Condition Notification 3.Interactive Applications –Social Networking –Multimedia Content Exchange –Advertising

Geographic Routing – Overview Why Geographic Routing? – Events are locally relevant – Path is more important than Destination Identity & Position Reference – Relevance: Messages for specific target vehicles – Direction: Messages for on-coming vehicles only – Zone-based: Map is overlaid with a grid and divided into zones – Navigation-based: Route along specific road segments Packet Exchanges – KISS: DATA and ACK only – No Handshaking Sequence – Accept / Reject / Forward based on message and state info – Restricted Flooding Triggers – EVENT SEND_MSG RECV ACK – RECV_MSG DECISION ? ACCEPT : FWD_MSG : DROP_MSG

Broadcast Scenarios Highway Driving City Driving Rural Driving Path with Intermediate points Static Source Routing Radial Broadcast Bounding Box Controlled Flooding

Routing Bounding Boxes Rectangles Cones Circles Requires a systematic study

GrooveNet Protocol Details Network foundation - caters to each application category Packet Types and Exchange Sequences Addressing Packet Formats Route Search & Route Persistence Rules Route Table Representation State Information & Neighbor Interaction

GrooveNet Network Architecture Fast Path – Critical Messages Control Path – Route Update & Filtering PHY - Wireless Interface MAC - Firmware Linux - Device Driver Linux – Networking Stack: RT & Filter Linux – Networking Services Linux – Application Layer Delay A Delay B Delay C Delay D

Packet Types & Exchange Sequences DATA Packet with MESSAGE field –Critical Alerts –Non-Critical Updates –Subscribed Services ACK Packet (Optional) No Route Request, No Route Reply, No Route! Broadcast, Multicast and Unicast: DROP Rules Parse Message & Maintain State Information

GrooveNet Vehicle Addressing Message Type: Broadcast, Multicast, Unicast Filter Array: 1.Logical: I want to talk to Buick FJF Geographic: Message for Downtown Warren 3.Non-Geographic: If you have this capability…. i.Hop count: Message for - All cars within 6 hops radius ii.Navigation: Message for - All cars headed for Exit 22 iii.Direction: Message for - All neighbors driving east on I-90 iv.Speed: Message for - All cars moving within +/- 8mph of my speed v.Connectivity: Message for ANY mobile gateway

Route Search and Route Persistence Rules Scope: Region of Validity for each packet Path with intermediate hops (optional) Greedy Routing Message Lifetime Retransmission frequency and event Nodes moving in opposite direction Forward packets Periodic HELLO Messages for Neighbor identification

GrooveNet – Scalability & Performance On Road Testing –Implement in Linux as a kernel module Congestion Analysis –Route Virtual Vehicles over Map with actual protocols –Test for (a) Safety Alerts and (b) Congestion Probes Basic Connectivity Analysis –Test-bed with straight road –Determine end-to-end throughput & delay –Given speed distribution, max num nodes, density distributions

Simulation Demo Audio + Video Send Alerts! View Network at Runtime Playback logs GPS Info Network Connectivity

Simulation Demo Over 1000 simultaneous vehicles simulated!

Experimental Ad Hoc Test-bed Mobile Node Internet V Remote Monitoring of Experiment 1XRTT Cellular Data Network GPS Differential GPS reference station beacons 1.Vehicle-to-Vehicle Multi-hop 2.Vehicle-to-Mobile Gateway 3.Vehicle-to-Infrastructure 5.9 GHz DSRC Dedicated Short Range Communications Between vehicles

GrooveNet Test Kit 5.8 GHz ANTENNAS GPS ANTENNA LAPTOP COMPUTER w/ RADIO CARD HEADPHONES W/ MICROPHONE GPS RECEIVER POWER CORD (12 DC) WEB CAM Driven 5 vehicles over 400 miles – Urban, Rural and Highway Over 625,000 link measurements

Average Signal Attenuation vs. Distance Log-Distance Path Loss Model (P R (d) [dBm] = P R (d o ) – 10nlog 10 (d/d o )) Current data analysis suggests a path loss exponent of approximately 2 Residential (Suburban) Environments (Pittsburgh, PA)

Packet Error Rate vs. Distance Residential (Suburban) Environments (Pittsburgh, PA) Packet Error Rate generally less than 10% at distances approaching 100 m Large PER spike at ~ 10 m currently not understood

Packet Error Rate vs. Absolute Speed Residential (Suburban) Environments (Pittsburgh, PA) Packet Error Rate generally less than 10% at speeds up to 30 MPH No observed difference between effects of transmitter and receiver speed

Packet Error Rate vs. Relative Speed Residential (Suburban) Environments (Pittsburgh, PA) Packet Error Rate generally less than 10% at speeds up to +/- 30 MPH Relative speed does not appear to have a significant effect on PER values

Summary and Conclusions The Time has come for Vehicular Networking –Several Killer Apps! – Safety, Congestion Probing, Collaborative Driving, Ads Robust Vehicular Networking Test-bed –Extensive on Road Testing with over 400 miles logged GrooveNet Software Simulator –Realistic & Scalable with both real and virtual vehicles Network & Wireless Channel Performance Analysis –Encouraging Results with DSRC equipment!

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